This invention relates to improved devices responsive to changes in inclination, and desirably also responsive to changes in directional orientation with respect to the earth's magnetic field or another ambient field.
Various types of inclinometers have been proposed in the past for use in wells or other environments in which it is desirable to determine accurately the tilt or inclination of a device with respect to the vertical. One common type of inclinometer utilizes photographic equipment for actually taking a picture of a pendulum actuated inclination responsive unit in a well. Such equipment, however, has several disadvantages, including the requirement that the equipment be withdrawn completely from the well in order to read the photograph. Other devices have utilized strain gauges or the like for responding to forces developed in a weighted structure when it tilts from a normal vertical position, as for instance in U.S. Pat. No. 3,791,043. In the apparatus of that patent, inclination response is obtained by such strain gauges, while response to changes in directional orientation of the device with respect to the earth's magnetic field or another ambient field is achieved by a flux gate assembly subjected to that field. Such an assembly may include coils flux linked to a core or cores of paramagnetic material driven periodically to a magnetically saturated state by a periodically fluctuating electrical current, preferably an alternating current, which energizes a portion of the coil structure. A part or all of the coil structure responds to the saturation by producing the desired output representing the direction of the ambient magnetic field. My co-pending application Ser. No. 736,126, filed Oct. 27, 1976, shows another such flux gate arrangement, in which the core desirably takes the form of a ring of paramagnetic material, rather than two pairs of mutually perpendicular cores as in U.S. Pat. No. 3,791,043.